Mars Radiation Dosage Makes Life Improbable, Even with Global Flooding
An upcoming (June) paper in Icarus1 states, “ The biologically damaging solar ultraviolet (UV) radiation (quantified by the DNA-weighted dose) reaches the martian surface in extremely high levels.” Earth has an ozone layer and global magnetic field to shield out the damaging rays, but Mars has no known atmospheric filter. “Therefore, the existence of life on Mars, at least at the surface, cannot be considered as probable.”
The European authors compare the situation with Earth:
All known life forms on Earth share a common feature: their genetic information is coded in a DNA or RNA chain of nucleotides. When exposed to sufficiently high levels of UV radiation these chains are damaged. Therefore, organisms must either have UV protection mechanisms or efficient repair processes. (Emphasis added in all quotes.)
(For a recent study on these repair processes, see this 05/18/2005 story.) The researchers argue that the only likely place to look for putative Martian life forms would be a meter under the polar ice. Even there, however, the radiation is only reduced to terrestrial levels, not eliminated. Error correction would therefore be a prerequisite for Martian life.
Another paper in the same issue of Icarus2 describes what effect large meteor impacts could have had on underground aquifers. “Based on the liquefaction limit proposed for Mars (Fig. 2A), we suggest that impacts producing craters with diameters of 100 km or greater may have caused global occurrence of liquefaction and streamflow,” they say. They estimate there may have been around 1500 such impacts. Each one could have produced “violent eruption of groundwater” producing catastrophic floods and erosion of outflow channels, assuming “a saturated aquifer of global extent may have been present beneath a few km of frozen ground.” Impacts could have produced these effects “at great distances from the impact site.” If a mile-thick aquifer existed under the surface, they estimate that tens of thousands of cubic miles of water could be released from a single large impact.
1Cordoba-Jabonero et al., “Radiative habitable zones in martian polar environments,” Icarus, Volume 175, Issue 2, June 2005, Pages 360-371, doi:10.1016/j.icarus.2004.12.009.
2Wang et al., “Floods on Mars released from groundwater by impact,” Icarus, Volume 175, Issue 2, June 2005, Pages 551-555, doi:10.1016/j.icarus.2004.12.003.
Short-lived water flowing on Mars is not going to help get life going. In the first place, the mineralogy shows that Mars water was poisonous (see 01/05/2005 entry). In the second place, if the probability of getting one useful protein by chance is astronomically small (see online book), the chance of getting error-correction mechanisms to emerge in time for life to survive the radiation bath is absurdly, ridiculously out of the question. We saw that amino acids have a half-life of eight hours in a Martian environment (see 01/28/2005 story). Do the logic: if error-correcting life is ever found on Mars, it did not arise by chance.
“Violent eruptions of groundwater” – Hmmmm… did Mars have “fountains of the great deep”?